Technical Field
The disclosure concerns the production of rotating microwaves in a plasma reactor chamber.
Background Discussion
In one approach for generating rotating microwaves in a plasma reactor chamber, microwaves are radiated into a cylindrical cavity from two ports separated spatially 90 degree. By setting a temporal phase difference between the microwaves from the two ports at 90 degrees, the TE111 mode in a cylindrical cavity is rotated circularly with feedback control by two monitoring antennas, providing a plasma profile of high uniformity.
In another approach for generating rotating microwaves, temporal phases between the two microwaves radiated from the two ports are kept in phase. To produce rotation, an amplitude of the microwaves from one port is modulated in the form of A sin Ωt, while an amplitude of microwaves from the other port is modulated in the form of A cos Ωt. Here, Ω is an angular frequency of order of 1-1000 Hz, which is much smaller than that of a microwave carrier frequency of order of over 1 GHz. This dual injection rotates the TE111 mode at a slow frequency Ω so as to slowly agitate a localized plasma, spreading the plasma into a wider area to further increase a uniforminy of plasma distribution, particularly at high pressures.
However, the fast and slow rotations were provided only for the TE111 mode. There is a need to provide such rotation for any mode, not just the TE111 mode.